Cluster in WAN

[Marc Remolt]

Hi everybody,
as I haven't found much usefull information about clustering mysql in a WAN, I'd like to ask some questions.
Let me describe my intended setup first:
I'd like to increase the availability of a MySQL driven web application by simply running it on two servers. If those two servers are in the same subnet, I'd gain availability with server problems, but not, if the network dies (router ...). So I thought it would be a good idea to put the two machines in different locations, if possible even on different backbones.
What I do now is the usual replication which has the known disadvantages. The users can't just go to any of the two websites and make updates to the DB, I can have only one online at a time or risk async data. A cluster behind the two sites would result in me not having to care about that problem.
Now my questions:
The little I've found about this topic suggested, that clustering over the Internet could bring performance problems. The sites aren't under heavy load, maybe 5 writes/minute on average. Would that work over let's say a 2Mbit connection?
The second thing is security. Is there any way to encrypt the cluster communication? I was thinking about stunnel or simmilar products, but I'm not quite sure this will really work out. Any experience with this or any ideas?

Thanks for you bearing with me.

Marc